Magnesium-lithium base alloys



April 17, 1956 J. H. JACKSON MAGNESIUM-LITHIUM BASE ALLOYS 2 Sheets-Sheet 1 Filed Aug. 7, 1948 OOQO- ooQN ooo..

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ATTORNEYS April 17, 1956 J. H. JACKSON 2,742,357

MAGNESIUM-LITHIUM BASE ALLOYS Filed Aug. 7, 1948 2 Sheets-Sheet 2 A N. (-HET Ol HEAT NO. 3

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AGING TIME ALLOYS SOLUTIGN TREATED PRIOR TO AG|NG TREAMENT O in ATTORNEYS United States Patent O" 2,742,357A MAGNEsIUM-LrrHIUM BASE ALLOY John H. Jackson, Columbus, Ohio, assignor, by mesne assignments, to Mathieson Chemical Corporation, New York, N. Y., a corporation of Virginia Application August 7, 1948, Serial No. 43,057

` 1 Claim. (c1. 75L-16s) Thisinvention relates to magnesium-lithiumv alloys and has Vfor its object the provision of an improved alloy consisting essentially of a magnesium-lithium base, Aone or more of the alloying metals aluminum, cadmium, silver and-zinc, and one or more minor addition elements.

The alloys of my invention comprise 66% lor more of magnesium, from 1 to 13.5% of lithium, and oneor more of the aforementioned alloying metals, and one or 2,742,357 .Painted Apr. 17, 1956 ,in providing work-hardenable magnesium-lithium Ybase alloys.

I have also made the amazing discovery that the benecial effects of one or only a few 'slightly soluble elements in minor amounts can be enhanced by adding a large number of such elements. An alloy to which twenty- Y nine minor elements were added was produced with the amazing result of a signiiicant improvement in the `stability of the age-hardened alloy as measured by agehardening tests.`

The following are typical examples of alloy compositions including one or more minor elements:

Alloys ycontaining "minor additions are also creep resistant at room temperature.

It has been found that one `or more of the alloying metals are veryeffective in making the binary magnesiumlithium matrix Work hardenable and more creep resistant at room temperature. However, where the alloying metals are added in quantities appreciably greater than their solid solubility limits, at ordinary temperatures, it has been found that the effect is not lasting because of precipitation of the metal or a compound of it at temperatures up to and including 200 F.

In furtherance of the objective concept of the invention, certain of the foregoing elements were added to alloysl of the magnesium-lithium base and put into solution by a high-temperature solution treatment and it was found that the matrix was capable of work-hardening No Mg/Li Percent Percent Percent Percent Percent Percent Percent Percent Percent Percent Percent Percent n Mg Li Ag Cd n i u Ba a Al Mn Sn 5 80.8 13.5 1 4 0.25 0 0.16 0.1 0. 05 0.15 5 80.7 13.5 1 4 0.25 0.1 0.16 0.1 0. 05 0.15 6 80.8 13.5 1 ,4 0.25 0.1 0.15 0.0 0. 05 0.15 6 81.7 13.0 0 4 0.25 0.1 0.16 0.0 0. 05 0.15 8.1 83.8 10.4 1 4 0.25 0. 05 0.15 0.1 0. 05 0.15 8.1 83.8 10.4 1 4 0.25 0.1 0.16 0.1 0.00 0.15 6 67.8 11.3 5 15 0.25 0.1 0.16 0.1` 0. 05 0.15 6 57.8 11.3 5 15 0.15 0.2 0.24 0.2 0.10 0.15 6 69. 5 1l. 6 3 l5 0.25 0.1 0.16 0. 1 0. 05 0. 15 5 66.2 11.0 2 20 0.25 0.1 0.16 0.1 Y 0.05 0.15 76. 3 12.7 6 4 0. 51 0.13 6 75.9 12.6` 6 4 0.63

75.6 12.8 4 4 0.25 0.1 0.16 0.1 0. 05 2 6 77.5 12.7 4 4 0.5 0.25 2 6 73.5 12.2 4 4 4 all elements listed in column 1 more of the following minor addition elements in the In the accompanying drawings, Figs. l and 2 are approximate amounts given: n graphs on semi-logarithmic scales illustrating age-hardenv 0.16% Cu 0 0i% Ti ing characteristics of the invention.

0 05% Ca 0.01% V In Fig. 1 a comparison of the 150 F. age-hardening 0.10% Ni 0 01% Zr characteristics of (a) a 6 Mg/Li, 4% Zn, 4% Cd, 4% Ag 0.15% A1 0,01% C1- alloy, (b) the same alloy with small additions of Cu, 0 10% Ba 0 01% Ce 4,5 Ca, Al and Ba, and (c) the same alloy containing small 0.50% In 0.01% Mn amounts of 29 addition elements is given. The superi- 0.50% T1 0 01% Fe ority of alloys (b) and (c) is obvious. It should be 0 50%6Hg 0.01% C0 noted further that alloy (c) represents a marked im- 010/5 Sn 0 01% Cb provement over alloy (b) as is shown below: 0.01% Be' 0.01% Mo 60 0.01% Si 0.01% Ta Alloy Alloy 0.01% Sb 0.01% W b c 0.01% Te 0.01% Th Maximum Hardness 93 97 0'01% Pl.) 0 01% Sr 55 'llme at maximum hardness, hours 80 140 0.01% B1 Illme at hardness of 85 Rockwell E or over, hours.. 350 800 09e o? the important features of 11183110 0f my qniesfios. Iil if 300 66o vention 1s that they are work-hardening alloys which Fig. 2 shows the etect of Vdecreasing the silver content as evidenced by the age-hardening characteristics of a 6 Mg/Li, 15% Cd, 5% Ag alloy. Curve (1) shows the characteristic of a 6 Mg/Li, 15% Cd, 5% Ag alloy and the deleterious effect of decreasing the silver content is observable by comparing curve (1) with (2) which shows the characteristics of a 6 Mg/Li, 15% Cd, 3% Ag alloy. However, as evidenced by curve (3), this deleterious effect can be compensated for by small additions of a number of addition elements so as to produce an alloy having the following composition: 6 Mg/Li, 15%Cd, 3% Ag, 0.16% Cu, 0.05% Ca, 0.25% Zn, 0.10% Ni, 0.15% Al, 0.10% Ba. It will be readily seen that the stability of age-hardenable alloys may be achieved at y by adding a number of valloying elements in small amounts. v Y

Several melting procedures have proved satisfactory Vfor producing the `alloys 'of the invention. Y For example, melting'rnay be done under argon, Without flux, Vand in this event the metals are melted irst and the rnonmetallic compounds added subsequently. In an alternative procedure, the melting is done under a 75% HCl- 25% LiFuX in a single Crucible. A third melting procedure which has proved satisfactory requires two cruciles, some of the Y'components being added in a metallic state under theux with the magnesium-lithiumpin one crucible, and the other components being added asc'ompounds to a flux in a second crucible and the contents of this second -crucible are later transferred to the rst Crucible for linal alloying. f .InV producing the alloys under argon, it is important that the metals be relativelypure and especially low in sodium because the finished alloy should contain less than 0.1% of sodium as explained inthe application of Alfred C. Loonam, Serial No. 602,171, now U. S. Patent No. Y

2,453,444. When the alloy is produced under the LiCl-LiF flux, it is important that the ux as initially used be free of sodium to the end that it will absorb sodium from the alloy and `thus reducethe sodium to amounts less that 0.1% as explained in the application of Alfred H. Hesse, Serial No. 603,749, now U. S. Patent No. 2,507,713.

Y page 255, (1946).

Co., London.

I cl'aiin: Y, A magnesium-lithium base alloy, containing less than 0.1% of sodium, consisting of at least 66% of magnesium; from 1% to 13.5% 0f lithium; from 1% to 5% of silver; from 4% to 20% of cadmium; from 0.15% to 0.25% of zinc; from 0.05% to 0.2% of nickel; from 0.16% to 0.24% vof coppergvfr'om 0.1% to 0.2% of barium; from 0.05% to 0.10% of calcium; and from 0.15% to 2% of aluminum.

References Cited in the file of vthis patent UNITED STATES PATENTS Dean et al. ..Y v e f May 29, 1945 OTHER VREFERENCES Gann et al.: Magnesium and Its Alloys, reprinted 'from Industrial and Engineering Chemistry, vol. 19, page ll93, Oct. 1927, published by A. C. S., page 2, table I 'of reprint.

Hume-Rothen, Equilibrium Relations and Some Properties of Magnesium-Lithium and Magnesium-Silver- Lithium Alloys, I. Institute of Metals, vol. 71, 1945, pp. 589-601. Y

. Mellor: Inorganic and Theoretical Chemistry, vol. 4, Published by Longmans, Green and 

